I've been running the Cyanogenmod nightlies on my device. If I remember correctly, I was running the nightly from 2014-09-07 (7th of September).

Yesterday I flashed the M10 release without totally understanding what it was all about. I thought it was newer than the nightly but apparently not.

My phone is now stuck in a bootloop. It boots all the way to the home-screen for split second and the whole process repeats all over again.

I've messed this up real bad and don't want to lose all my data. Is there a way I can fix this? Can i just side-load the latest nightly and flash it onto the device or do I flash the same nightly that I was running?

This sort of question has been asked so many times before but I couldn't find one that explains how to resolve this. Thank you.

As you've used the boot-loop tag: Have you checked with its tag-wiki? Do the pointers help you with your case? If that didn't solve the issue: What have you tried, and where are you stuck? If you've solved the issue: Be welcome to answer your own question to share your solution and experience. Thanks!
– Izzy♦Sep 17 '14 at 8:45

Yes I've checked the tag-wiki. I even cleared my cache and my davik-cache from the recovery but the bootloop continues. I know it's not an app-related issue; it was the ROM I flashed. Now all I need to figure out is whether to reflash a newer one or the same one to resolve this? Thx.
– Mridang AgarwallaSep 17 '14 at 9:15

It could also be the data of some app which is in the way, if it's a "core app" needed to run the system, so a factory-reset might be required. Of course, you could also boot into recovery and try deleting the app directories below /data/data one by one (i.e. delete one, reboot to see if the problem is gone, if not repeat with the next) to avoid a complete reset – which can be compared to the "delete data" button in "manage applications". The corresponding apps would re-create their directories then.
– Izzy♦Sep 17 '14 at 9:22